Struggling to get 16x2 I2C display to work

Hi there,

I'm so close to completing my SamplerBox build and it's gonna be so sweet when it's up and running, but I'm struggling to get a display working so I can see what patch I have loaded. I'm in wayyyy over my head - I've never really tried any electronics or computing stuff before in my life beyond being a mild power-user on my computers - and I've been going round in circles these last couple of weeks with this display. I'm pretty sure I've read every forum post on here containing the words display and I2C! Essentially when powering up the Pi with SamplerBox loaded, all I get is squares on the top row with no backlight.

I've got this module here which I've got working on a standard installation of Raspberry Pi OS using their demo files - see here. I've activated I2C in the boot settings and I think I've found the address to be 0x3e which I've put into configuration.txt like so:
USE_I2C_LCD = True (have tried 16x2 as well as per a couple other threads I read but to no avail)
I2C_LCD_ADDR=0x3e (I've also tried 0x60 as that came up in i2cdetect, as well as a bunch of other addresses I found for similar displays like 0x27, 0x3f, 0x70 etc. which didn't work either of course!)

I've tried digging through forum posts both here and elsewhere but my guess is there's something I've not done that would be apparent to someone who actually knows how to program a computer! Any suggestions or help would be amazing. I'm using a Raspberry Pi 4.

If you're interested, this will replace my old Akai MPX16, a horrendously slow and cumbersome device that I've been struggling along with for too long. It finally died after a tour last year leading me to find SamplerBox which I can't wait to take on the road. I really appreciate all the work that's gone into creating SamplerBox over the years, what a fantastic project!

Cheers gang,
skelmins

Hi Skelmins,

The I2C_lcd.py script/module is specifically aimed at the HD44780 chips.

If I read the docs of your display correctly, it has a AiP31068L chip combined with PCA9633 chips for controlling the colours.
The first one is the most important one (not able to configure colours is a cosmetic shortcoming).
And it seems not to be compatible (the 03e address already raises eyebrows as it is not mentioned in the configuration.txt as a possibility, but OK one never knows).

So - if I'm right -  the bad news is a choice between:

1. create module to support this display..
   
2. get a supported display..
   
3. use the webgui..
   

The first option is doable, since the demo in your links includes a python driver script. This can be extended & merged in samplerbox with some creative tweaking.
If you're not familiar with this level of programming it will be hard to do - or an interesting experience to put it positively.
I may be able to give you a kickstart (given that your samplerbox is functioning OK except for the display and you can connect it to your home network = you can access it from your PC/laptop).

Please share your thoughts..

Regards, Hans

Hi Skelmins,

The I2C_lcd.py script/module is specifically aimed at the HD44780 chips.

If I read the docs of your display correctly, it has a AiP31068L chip combined with PCA9633 chips for controlling the colours.
The first one is the most important one (not able to configure colours is a cosmetic shortcoming).
And it seems not to be compatible (the 03e address already raises eyebrows as it is not mentioned in the configuration.txt as a possibility, but OK one never knows).

So - if I'm right -  the bad news is a choice between:

1. create module to support this display..
   
2. get a supported display..
   
3. use the webgui..
   

The first option is doable, since the demo in your links includes a python driver script. This can be extended & merged in samplerbox with some creative tweaking.
If you're not familiar with this level of programming it will be hard to do - or an interesting experience to put it positively.
I may be able to give you a kickstart (given that your samplerbox is functioning OK except for the display and you can connect it to your home network = you can access it from your PC/laptop).

Please share your thoughts..

Regards, Hans

Hey Hans,

Thanks for the reply, that makes a lot more sense now. I confused myself with the I2C interface thinking it made it a universal sort of thing and missed the different controller chips in the documentation.

Based on what you've said, I imagine the easiest thing to do would be to grab a supported display and save myself the interesting experince (  ) and see if I can return or sell on the current display. It's very good of you to offer to help set me on my way to coding a new module though and I appreciate that, thank you!

Looking on ebay I've found a module that seems to have the right addresses and chip number now I know better what I'm looking for - it's an HD44780 compatible display with an I2C backpack. Specs below. A quick glance over to confirm would be amazing to save myself more head scratching.

Specifications
Display: 16 columns × 2 rows (HD44780 compatible)
I²C Backpack: PCF8574 (typical addresses: 0x27 or 0x3F)
Operating voltage: 5V (SDA/SCL often tolerant to 3.3V)
Backlight: Blue LED (on/backlight control via backpack)
Dimensions: ~80 × 36 mm (module dependent)

Cheers,

Skelmins

Hi Skelmins,

OK, fair choice.
The specs as you state them look OK, so that's a fast bypass.

And yes, a bit of bad luck. When it gets to low level hardware stuff, it's easy to take a turn needing more effort than you're waiting for. I have to admit I had to look twice and dig in the device supplied code before I realized what was blocking your setup.

Anyway: more luck this time &  have fun !
Regards, Hans

Success! Now to build a nice stage-ready box for it all to go in. Thanks again for your help, and for making this whole thing possible ✌️